Conventionally, adapters are used as power supply for electronic devices (for example, laptop). If communication is needed between an adapter and an electronic device, extra wires are required to be added in a power cord between the adapter and the electronic device. In this way, BOM (bill of material) cost which is more and more sensitive for people will increase, and the power cord will become heavier and thus difficult to be carried, especially in the application of low power.
Generally, as shown in FIG. 1, an adapter is connected to an electronic device via an output cable including Vo, GND and ID wires inside. The Vo and GND wires are power lines, and the adapter provides power to the electronic device through these power lines. In the art, when the adapter and the electronic device are connected, communication therebetween is set up through the ID wire. The electronic device can read some fundamental information of the adapter, including manufacturer, date of manufacture, and the maximum power it can supply. Such information is written into the adapter in advance. Thus, when the conventional adapter communicates with the electronic device through the ID wire, the transmitted information is simple and fixed, but cannot be changed and adjusted.